Enhanced removal of hemicelluloses from cellulosic fibers by poly(ethylene glycol) during alkali treatment

Enhancing removal of hemicelluloses from cellulosic fibers is of decisive importance for producing high-purity cellulose. In this study, poly(ethylene glycol) (PEG) was added to a cold caustic extraction (CCE) process to promote removal of hemicelluloses from a softwood sulfite dissolving pulp. The content of hemicelluloses was considerably decreased from 11.4 % in the original sample to 5.3 % in the PEG/CCE-treated sample under the studied conditions. This positive result of PEG addition can be explained by (1) improved inward penetration and diffusion of NaOH into the fiber structure and outward diffusion of hemicelluloses from the fiber structure to the bulk phase, and (2) enhanced fiber swelling due to inclusion of PEG in the fiber walls and improved NaOH diffusion. Moreover, the effects of PEG/CCE treatment on the distribution of hemicelluloses in the fiber walls and the molecular weight of the residual hemicelluloses in the resulting pulp were investigated.